A New Treatment For Improving The Use Of Dietary Sugar For Energy Purposes

ABSTRACT

A method comprising, receiving digital-electrical input symbols of a stream of input symbols, the input symbols corresponding to signal points of a symbol constellation. The method also comprises classifying the input symbols, wherein a first symbol class comprises input symbols corresponding to signal points that are variant to rotation of the symbol constellation, and, a second symbol class comprises input symbols corresponding to signal points that are invariant to rotation of the symbol constellation. The method also comprises applying selective differential coding only to those input symbols of the first symbol class.

This application claims the benefit of U.S. Provisional Application Ser.No. 62/063,671, filed by Chongjin Xie on Oct. 14, 2014, entitled“DIFFERENTIAL-CODING AND DECODING FOR QUADRATURE DUOBINARY COHERENTOPTICAL COMMUNICATION SYSTEMS” incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The invention relates, in general, to optical communication systems andto methods of using and manufacturing such systems.

BACKGROUND OF THE INVENTION

This section introduces aspects that may help facilitate a betterunderstanding of the inventions. Accordingly, the statements of thissection are to be read in this light and are not to be understood asadmissions about what is prior art or what is not prior art.

Polarization-division-multiplexed (PDM) quadrature duobinary (QDB)modulation with digital coherent detection has promise for use in highspeed (e.g., 100 Gb/s or higher) optical communication. One problem withthe coherent detection of QDB modulated signals is that cycle-slip cancause catastrophic error propagation. As understood by those skilled inthe art cycle-slip can occur when the phase of the optical carrieroutput by a laser, e.g., a continuous sinusoidal wave signal, wanders.

Efforts to reduce error propagation in coherent detection when using PDMQDB modulation have attempted to recover the absolute carrier phaseusing periodically inserted pilot symbols in the transmitted data.Recovering the absolute carrier phase in this manner, however, canrequire more complex carrier phase recovery units and can reduce thespectral efficiency due to the insertion of pilot symbols into thetransmitted data stream.

SUMMARY OF THE INVENTION

One embodiment is a method. The method comprises, receivingdigital-electrical input symbols of a stream of input symbols, the inputsymbols corresponding to signal points of a symbol constellation. Themethod can also comprise classifying the input symbols. In some suchembodiments, a first symbol class comprises input symbols correspondingto signal points that are variant to rotation of the symbolconstellation, and, a second symbol class comprises input symbolscorresponding to signal points that are invariant to rotation of thesymbol constellation. The method can also comprise applying selectivedifferential coding only to those input symbols of the first symbolclass.

In any embodiments of the method, the symbol constellation can be aquadrature duobinary constellation. In any embodiments of the method,the first symbol class can include symbols [0,1] and [1,0], and thesecond symbol class can include symbols [0,0] and [1,1]. In anyembodiments of the method, the differential coding can be applied to theinput symbols according to a differential coding rule, thereby producingdifferential-coded symbols. In any embodiments of the method, if a givensymbol in the first symbol class is equal to an immediately precedingsymbol in the first symbol class, then the given symbol can be coded as[1,0], and, if the given symbol is not equal to the immediatelypreceding symbol in the first symbol class, then the given symbol can becoded as [0,1].

In any embodiments of the method, the symbols of the stream of inputsymbols can be precoded prior to the selective differential coding fortransmission of an output optical data stream in an opticalcommunication system. In any embodiments of the method, the inputsymbols can include two bits [DI_(n), DQ_(n)], where n is a symbolindex, and the symbols can be precoded according to: PI_(n)=XOR(DI_(n),PI_(n−1)) and PQ_(n)=XOR(DQ_(n), PQ_(n−1)) and, BI_(n)=PI_(n)+PI_(n−1)−1and BQ_(n)=PQ_(n)+PQ_(n−1)−1, the precoded symbol being [BIn, BQn].

Any embodiments of the method can further comprise receiving an opticalsignal carrying an optical stream of input symbols. Any embodiments ofthe method can further comprise converting the optical stream to thedigital-electrical input symbols. In any embodiments of the method, theselective differential coding can produce a stream ofselective-differentially-decoded symbols, and can further comprisepost-coding symbols of the selective-differentially-decoded symbolstream. In any embodiments of the method, theselective-differentially-decoded symbols can each include two bits[BI_(n),BQ_(n)], where n is a symbol index, and theselective-differentially-decoded symbols are post-coded according to:DI_(n)=1−|BI_(n)| and DQ_(n)=1−|BQ_(n)|, the post-coded symbol being[DI_(n),DQ_(n)].

Another embodiment is an apparatus. The apparatus comprises a digitalsignal processor (DSP) configured to receive digital-electrical inputsymbols of a stream of input symbols, the input symbols corresponding tosignal points of a symbol constellation. The apparatus can also comprisea symbol classifier configured to classify the input symbols. In anysuch embodiments, a first symbol class comprises input symbolscorresponding to signal points that are variant to rotation of thesymbol constellation, and, a second symbol class comprises input symbolscorresponding to signal points that are invariant to rotation of thesymbol constellation. The apparatus can also comprise a selectivedifferential encoder configured to apply selective differential codingonly to those input symbols of the first symbol class.

In any embodiments of the apparatus, the symbol constellation can be aquadrature duobinary constellation. In any embodiments of the apparatus,the first symbol class can includes symbols [0,1] and [1,0], and thesecond symbol class can include symbols [0,0] and [1,1]. In anyembodiments of the apparatus, the DSP can be configured to precode thesymbols of the stream of input symbols prior to the selectivedifferential coding for transmission of an output optical data stream inan optical communication system. In any such embodiments of theapparatus, the selective differential coding can be applied to the inputsymbols according to a differential coding rule, thereby producingdifferential-coded symbols. In any embodiments of the apparatus, if agiven symbol in the first symbol class is equal to an immediatelypreceding symbol in the first symbol class, then the given symbol can becoded as [1,0], and, if the given symbol is not equal to the immediatelypreceding symbol in the first symbol class, then the given symbol can becoded as [0,1]. In any embodiments of the apparatus, the input symbolscan include two bits [DIn,DQn], where n is a symbol index, and thesymbols are precoded according to: PI_(n)=XOR(DI_(n), PI_(n−1)) andPQ_(n)=XOR(DQ_(n), PQ_(n−1)), and, BI_(n)=PI_(n)+PI_(n−1)−1 andBQ_(n)=PQ_(n)+PQ_(n−1)−1, the precoded symbol being [BI_(n),BQ_(n)].

Any embodiments of the apparatus can further comprise anoptical-to-electrical converter configured to convert a received opticalsignal carrying an optical stream of input symbols to thedigital-electrical input symbols. In any such embodiments, the selectivedifferential coding can produce a stream ofselective-differentially-decoded symbols, and can further comprisepost-coding symbols of the selective-differentially-decoded symbolstream. In any embodiments of the apparatus, theselective-differentially-decoded symbols can each include two bits[BI_(n),BQ_(n)], where n is a symbol index, and theselective-differentially-decoded symbols can be post-coded according to:DI_(n)=1−|BI_(n)| and DQ_(n)=1−|BQ_(n)|, the post-coded symbol being[DI_(n),DQ_(n)].

Another embodiment is an optical communication system. The systemcomprises an optical-to-electrical converter configured to convert areceived optical stream of symbols to a digital-electrical stream ofreceived symbols, the received symbols corresponding to signal points ofa symbol constellation. The system can also comprise anelectrical-to-optical converter configured to convert adigital-electrical stream of transmitted symbols to a transmittedoptical stream of symbols. The system can also comprise a digital signalprocessor. The digital signal processor can be configured to classifythe received symbols and the transmitted symbols. In any such embodimenta first symbol class can comprise symbols corresponding to signal pointsof the symbol constellation that are variant to rotation of the symbolconstellation, and, a second symbol class can comprise symbolscorresponding to signal points of the symbol constellation that areinvariant to rotation of the symbol constellation. The digital signalprocessor can also be configured to apply selective differential codingonly to those input symbols of the first symbol class. In anyembodiments of the system, the symbol constellation can be a quadratureduobinary constellation.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the disclosure are best understood from the followingdetailed description, when read with the accompanying FIGUREs. Somefeatures in the figures may be described as, for example, “top,”“bottom,” “vertical” or “lateral” for convenience in referring to thosefeatures. Such descriptions do not limit the orientation of suchfeatures with respect to the natural horizon or gravity. Variousfeatures may not be drawn to scale and may be arbitrarily increased orreduced in size for clarity of discussion. Reference is now made to thefollowing descriptions taken in conjunction with the accompanyingdrawings, in which:

FIG. 1A illustrates an example constellation diagram for QDB modulation;

FIG. 1B presents a symbol map corresponding to the example constellationdiagram illustrated in FIG. 1A showing constellation points that aresusceptible to cycle slip;

FIG. 2A presents a flow diagram of an example differential-coding schemefor QDB modulation in accordance with the present disclosure;

FIG. 2B presents a flow diagram of an example differential-decodingscheme for QDB modulation in accordance with the present disclosure;

FIG. 3 presents an example chart showing selected steps in an examplemethod of differential-coding and differential-decoding for an examplestream of QDB symbols in accordance with method embodiments of thepresent disclosure such as the example embodiments presented in FIGS. 2Aand 2B;

FIG. 4 presents a block diagram of an example communication system usingQDB modulation with differential-coding and differential-decoding inaccordance with method embodiments of the present disclosure such as theexamples method presented in FIGS. 2A and 2B; and

FIG. 5 depicts a plot of bit-error-rate (BER) versus opticalsignal-to-noise ratio (OSNR) for an example simulated data signal usingdifferential-coding and differential-decoding operations for thesimulated data in accordance with the present disclosure such asdescribed in the context or FIGS. 2-4.

In the Figures and text, unless otherwise indicated, similar or likereference symbols indicate elements with similar or the same functionsand/or structures.

In the Figures, unless otherwise indicated, the relative dimensions ofsome features may be exaggerated to more clearly illustrate one or moreof the structures or features therein.

Herein, various embodiments are described more fully by the Figures andthe Detailed Description. Nevertheless, the inventions may be embodiedin various forms and are not limited to the embodiments described in theFigures and Detailed Description of Illustrative Embodiments.

DETAILED DESCRIPTION

The description and drawings merely illustrate the principles of theinventions. It will thus be appreciated that those skilled in the artwill be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of theinventions and are included within its scope. Furthermore, all examplesrecited herein are principally intended expressly to be for pedagogicalpurposes to aid the reader in understanding the principles of theinventions and concepts contributed by the inventor(s) to further theart, and are to be construed as being without limitation to suchspecifically recited examples and conditions. Moreover, all statementsherein reciting principles, aspects, and embodiments of the inventions,as well as specific examples thereof, are intended to encompassequivalents thereof. Additionally, the term, “or,” as used herein,refers to a non-exclusive or, unless otherwise indicated. Also, thevarious embodiments described herein are not necessarily mutuallyexclusive, as some embodiments can be combined with one or more otherembodiments to form new embodiments.

Embodiments of the disclosure mitigate cycle-slip induced errorpropagation for QDB modulated signals by using differential-coding anddifferential-decoding techniques as disclosed herein.

FIG. 1A presents an example 9-point constellation for a QDB modulatedsignal. As understood by one skilled in the pertinent art, a QDBmodulated signal can be represented by a constellation of nineconstellation points 105 with real and imaginary parts referred to asin-phase or I-axis (I), and quadrature or Q-axis (Q), componentsrespectively. As discussed further below each point 105 represents oneQDB symbol. Differential-coding and differential-decoding for QPSK(quadrature phase-shift keying), 16QAM (quadrature amplitudemodulation), 64QAM, and mPSK are not effective or applicable to QDBmodulated signals due, at least, to the latter's 9-point constellationformat. Each constellation point 105 is located at one of ninecoordinate values. In this discussion, constellation points arerepresented as I, Q pairs within parentheses, thus (I,Q)=(0,±1), (±1,0),(±1,±1) and (0,0).

FIG. 1B represents a QDB symbol map corresponding to the QDBconstellation of FIG. 1A. The symbol map includes four symbols, whichmay be represented as bracketed bit value pairs, or dibits, [0,0],[0,1], [1,0] and [1,1]. These values may be uniquely represented by thefirst quadrant of the symbol map, with the other quadrants providingredundant mapping of some symbols. Any of the symbols may be representedby an I/Q pair corresponding to the first quadrant. Thus the [1,1]symbol is represented by four degenerate points in the constellation,the [0,1] and [1,0] symbols are each represented by two degeneratepoints, and the [0,0] symbol is represented by a single point.

The differential-coding and differential-decoding techniques disclosedherein recognize that only certain classes of the QDB constellationpoints 105, and corresponding symbols, are subject to the aforementionedpropagation error caused by cycle slip.

Symbol classes are illustrated in FIG. 1B, in which the symbols aredivided into two classes. A second symbol class 110, referred to hereinas Class II symbols, is depicted as filled circles and correspond to QDBconstellation points for which a cycle slip may not cause an error. SuchClass II symbols can have symbol values of [1,1] or [0,0]. When a cycleslip includes an nπ/2 radian phase rotation, a symbol value of [1,1]remains [1,1] and a symbol value [0,0] remains [0,0], and therefore noambiguity in the symbol, and hence no error, occurs for the Class IIsymbols.

The Class II symbols may be described as being invariant to rotation.Symbols that are invariant to rotation are those symbols for which thesymbol value does not change when the constellation is rotated about areference point (e.g. the origin of the coordinate space of theconstellation) by an angle of rotational symmetry of the constellation.In the present example angles of rotational symmetry are represented bynπ/2.

The first symbol class 115, sometimes referred to herein as Class Isymbols, is depicted as open circles and correspond to QDB constellationpoints for which a cycle slip can cause an error. Such Class I symbolscan have symbol values of [1,0] or [0,1]. In contrast to Class IIsymbols, when a cycle slip involves, e.g., a π/2 or 3π/2 phase rotation,the constellation coordinate value (1,0), corresponding to symbol [1,0],will become (0,1) or (0,−1), corresponding to symbol [0,1]. Similarly,the constellation coordinate value (0,1), corresponding to symbol [0,1],will become (−1,0) or (1,0), corresponding to symbol [1,0]. In eitherexample, a Class I symbol error results. Accordingly, the Class Isymbols may be described as being variant to rotation.

Embodiments of the disclosure provide coding of optically transmitteddata to mitigate the effects of cycle slip. One such embodiment is amethod, e.g., a method of differential-coding and differential-decodinga PDM-QDB modulated signal, as performed in one or more digital signalprocessors (DSPs).

FIG. 2A presents a flow diagram of an example differential-coding method200A for QDB modulation in accordance with the present disclosure. FIG.2B presents a flow diagram of an example differential-decoding scheme200B for QDB modulation in accordance with the present disclosure. Invarious embodiments the method 200A may be performed by an opticaltransmitter, and the method 200B may be performed by an opticalreceiver. The illustrated embodiments show differential coding/decodingof a single polarization channel of a modulated optical signal. For aPDM-QDB signal, the signal at each polarization could be processed usingthe same steps as presented in the described methods.

With continuing reference to FIGS. 2A and 2B throughout, the method 200Acommences at a data input step 205 wherein the input data corresponds todigitized data, e.g., a stream . . . D_(n−1), D_(n), D_(n+1) . . . ofpairs of electrical binary-coded digital input values, e.g. symbols[D_(I),D_(Q)], to be transmitted through an optical communicationsystem. As discussed further below, a pre-coding operation 260 may beperformed on the input data symbols to produce a stream of pre-codedsymbols [B_(I),B_(Q)], . . . B_(n−1), B_(n), B_(n+1) . . .

The method 200A includes performing in a step 210, e.g. in a DSP, aclassification operation on the input symbols . . . D_(n−1), D_(n),D_(n+1) . . . The classification operation includes classifying theinput symbols as Class I or Class II symbols. The Class II symbolscorrespond to those symbols that are invariant to rotation, e.g. [0,0]and [1,1], corresponding in the present example embodiment to thoseconstellation points having I/Q values of equal magnitude, e.g.(I,Q)=(1,1) (−1,1), (1,−1), (−1,−1) and (0,0). The Class I symbolscorrespond to those symbols that are variant to rotation, e.g. [0,1] and[1,0], corresponding in the present example embodiment to thoseconstellation points having I/Q values on unequal magnitude, e.g.(I,Q)=(0,1) (1,0), (0,−1) and (−1,0).

The method 200A includes applying via steps 215, 217 and 220 adifferential coding operation to only the Class I symbols, to producedifferential-coded pairs of symbols, according to a differential codingrule. The differential coding rule is applied to each one of the Class Isymbols represented in the data-stream. According to the rule, in oneembodiment if a given Class I symbol in the symbol stream is the same asthe immediately preceding Class I symbol, the given Class I symbol iscoded in step 217 as [0,1]. And, according to the rule, if the givensymbol is different from the immediately preceding Class I symbol fromthe stream, then the given symbol is instead coded in step 220 as [1,0].In an alternate embodiment the given Class I symbol is coded in step 217as [1,0] and coded as [0,1] in the step 220.

As part of performing the differential coding rule, if the given(current) symbol under consideration in the differential codingoperation steps 215, 217, 220 is a first Class I symbol from thedata-stream, then coding of the first Class I symbol is not changed. Forinstance, if the coding for the first Class I symbol was [0,1] or[0,−1], then after step 215 the coding is retained as [0,1] or [0,−1],respectively.

As further illustrated in FIG. 2A, in some embodiments of the method200A, the Class II symbols, not subject to the differential codingoperation step 215, are held, e.g. buffered, in a memory of the DSP instep 225.

As also illustrated in FIG. 2A, in some embodiments of the method 200A,the Class I symbols held in step 225 and the differential-coded Class Isymbols in steps 217, 220, are recombined in step 230 in a manner thatre-establishes the order of data symbols as present in the input datastream in step 205.

As further illustrated in FIG. 2B, in some embodiments of the method200B, a choosing step 235 may receive the differential-coded symbols inthe recombined data stream (including the Class I symbols subject tosteps 215, 217 and 220), e.g. in an optical receiver. In the step 235the Class I symbols are selected for differential decoding. The selectedreceived symbols are subjected to a differential decoding operation instep 240. In some such embodiments of the method 200B, the symbols ofthe recombined data stream that were not differential-coded (e.g., theClass I symbols not subject to step 215 and previously held in step 225)are held, e.g. buffered without modification, in a memory of the DSP ora different DSP, in step 245.

In some embodiments, the differential decoding operation in step 240 isapplied to the differential-coded symbols to producedifferential-decoded symbols, according to a differential decoding rule.As part of performing the differential decoding rule in the step 215, ifeither the I or Q components of a later differential-coded (Class I)symbol has an absolute value that is the same as the absolute value ofthe corresponding I or Q component of the immediately precedingdifferential-coded symbol, then the later differential-coded symbol isdecoded as [0,1]. And, as part of performing the differential decodingrule, if both I and Q components of the later differential-coded symbolboth have absolute values that are different from those of theimmediately preceding differential-coded symbol, then the latterdifferential-coded symbol is decoded as [1,0]. In an alternative variantof the rule, if either I or Q components of the later differential-codedsymbol have absolute values that are the same as those of theimmediately preceding differential-coded symbol, then the laterdifferential-coded symbol is decoded as [0,−1]. And, according to thealternative variant of the rule, if both I and Q components of the laterdifferential-coded symbol have absolute values that are different from Iand Q of the immediately preceding differential-coded symbol, then theone differential-coded symbol is decoded as [−1,0].

Also as part of the performing the differential decoding rule, if thelater differential-coded symbol is a first symbol of thedifferential-coded symbols from the data-stream, then coding of thefirst symbol is not changed. For instance, if the coding for the firstof Class I symbols was [0,1] (or [0,−1]), then after step 240 the codingis retained as [0,1] (or (0,−1)], respectively.

As further illustrated in FIG. 2B, in some embodiments of the method200B, the differential-decoded symbols formed in step 240 and thenon-differential-decoded symbols held in step 245 are then recombined instep 250 in a manner that re-establishes the order of data symbols aspresent in the input data stream in step 205 and/or 235. The method 200Bstops at data output step 255.

As part of the differential coding operation in step 215 or thedifferential decoding operation in step 240, whether the in-phase andquadrature components of the Class I pairs of symbols areencoded/decoded as 1 or −1 depends on the immediately preceding symbolin the data-stream. The setting to 1 or −1 may be made to ensure thatthe level changes between the I components of adjacent symbols, and/orbetween the Q components of adjacent symbols, do not exceed unity. Someembodiments of the method 200A further include a pre-differential codingoperation in step 260 to convert binary data to duobinary data for eachquadrature of a QDB signal, having values of −1, 0, and 1. Thepre-differential coding operation in step 260 may be separatelyperformed, e.g. in the DSP, on all of the individual ones of the pairsof electrical digital input from step 205 prior to the classificationoperation step 210. That is, the symbols subject to the classificationoperation in step 210 are formed after the pre-differential codingoperation step 260.

The pre-differential coding operation step 260 is separately performedon the I components and on the Q components of the processed symbols. Insome embodiments, for example, the pre-differential coding operationstep 260 includes for each one of the I/Q pairs of input signals (e.g.,coded as binary symbols), DI_(n) and DQ_(n), to be represented as thein-phase and quadrature of QDB modulated signals, respectively, applyinga pre-differential coding rule in step 262:

PI _(n)=XOR(DI _(n) ,PI _(n−1)) and PQ _(n)=XOR(DQ _(n) ,PQ _(n−1))

wherein PI_(n) and PQ_(n) are intermediate pre-differential coded I/Qcomponents to represent the in-phase and quadrature QDB signals of then-th datum in the data-stream to be modulated, and wherein XOR is anexclusive logical OR operation. The pre-differential coding rule thenfurther includes applying a second pre-differential coding rule in step264:

BI _(n) =PI _(n) +PI _(n−1)−1, and, BQ _(n) =PQ _(n) +PQ _(n−1)−1

wherein BI_(n) and BQ_(n) respectively, correspond to thepre-differential coded in-phase and quadrature duobinary components forthe QDB modulated symbols corresponding to the electrical digital inputsymbols operated on in step 210.

Some embodiments of the method 200B further include apost-differential-decoding operation in a step 265 to convert duobinarydata to binary data for each of the I and Q components of a QDB signal.The post-differential-decoding operation in step 265 may be separatelyperformed, in the DSP or in a different DSP, on all of the individualones of the recombined data stream of symbols (e.g., from step 250) thatinclude the differential-decoded pairs of Class I symbols (e.g., decodedin step 240) recombined with the pairs of Class II symbols (e.g., heldin step 245).

In some embodiments, for example, the post-differential-decodingoperation step 265 includes for each one of the symbols representing therecombined data stream of symbols, applying a post-differential decodingrule:

DI′ _(n)=1−|EI _(n)| and DQ′ _(n)=1−|EQ _(n)|

wherein EI′_(n) and EQ′_(n) respectively, represent the in-phase andquadrature components of the data stream output by the step 240, andDI′_(n) and DQ′_(n) respectively, represent the in-phase and quadratureduobinary modulated post-differential decoded signals of the n-th datumin an output (e.g., binary data output) data-stream (step 255).

In some embodiments of the method 200A, the re-established data streamcontaining differential-coded symbols (step 230) may be transmitted viaan optical communication system, such as the system 400 discussed in thecontext of FIG. 4, below.

In some embodiments of the method 200A, the differential codingoperation (steps 215, 217, 220) is performed in the DSP of a transmittersubunit of the optical communication system. In some embodiments, theholding, the recombining and pre-differential coding operation steps225, 230, 260 are also performed in the DSP of the transmitter subunit.

In some embodiments of the method 200B, the differential decodingoperation (step 240) is performed in a different DSP of a receiversubunit of the same optical communication system or a remote opticalcommunication system. In some embodiments, the second holding, thesecond recombining and post-differential decoding operation steps 245,250, 265 are also performed in the different DSP of the same or remotereceiver subunit.

FIG. 3 presents an chart showing selected steps in an example method ofdifferential-coding and differential-decoding for an example data streamof QDB signals in accordance with a method embodiment of the such as theexample embodiment presented in FIGS. 2A and 2B.

FIG. 3 presents a data stream represented by a tabular presentation of16 symbols (n=16) of the data system. With continuing reference to FIGS.2A, 2B and 3 throughout, DI_(n) and DQ_(n) are respectively I and Qcomponents of input symbols of QDB signals from the input data to bemodulated presented in step 205. As illustrated in FIG. 3 as part ofpre-coding step 260, after the applying the first pre-coding rule (step262) the intermediate pre-coded symbols, [PI_(n),PQ_(n)], are generatedand after the applying the second pre-coding rule (step 264) thepre-coded symbols, [BI_(n),BQ_(n)], are generated. To facilitateperforming the second rule, a seed value is used as a 0-th symbol.

The classification step 210 is performed on the pre-coded symbols,[BI_(n),BQ_(n)]. The differential coding step 215 (including steps 217and 220) is performed only on the Class I symbols (n=4, 10-13 and 16),while the Class II symbols (n=1-3, 5-9, 14-15) are held in step 225.After differential coding (step 215) the Class I and II symbols arerecombined in step 230 to form the output symbol stream . . .[EI_(n−1),EQ_(n−1)], [EI_(n),EQ_(n)], [EI_(n+1),EQ_(n+1)] . . . Therecombined symbols may then be converted (e.g., via an into in-phaseoptical modulator) an optical and quadrature QDB modulated signals thatare transmitted over a long distance (e.g., kilometers), e.g., via anoptical fiber.

The optical symbols may then be converted (e.g., via anoptical-to-electrical receiver) back into digital electrical signals,component pairs that are equivalent to the recombined data stream ofsymbols [EI_(n), EQ_(n)] formed in step 230.

The recombined data stream of symbols [EI_(n),EQ_(n)] is subjected tothe choosing step 235, and the differential-coded pairs of symbols, theClass I symbols, are then subject to the differential decoding in step240 while the non-differential-coded symbols, the Class II symbols, areheld in step 245. After the differential decoding step 240 the Class Iand Class II symbols are then recombined in step 250 in a manner thatre-establishes the order of data symbols as present in the input datastream in step 205, thereby forming a stream of recombined differentialdecoding symbol pairs (EI′_(n),E′_(n)).

In step 265 the recombined differential decoding symbols(EI′_(n),EQ′_(n)) are subject to a post-decoding operation on all of thesymbols in the recombined data stream of symbols (e.g., from step 250)to form post-differential decoded symbols (DI′_(n),DQ′_(n)) that can beoutput at step 255.

Thus it is seen from FIG. 3 the input data may be recovered at theoutput after the coding and decoding processes described by FIGS. 2A/Band the related description.

Another embodiment of the disclosure is an optical communication system.FIG. 4 presents a block diagram of an example optical communicationsystem 400 using QDB modulation with differential-coding anddifferential-decoding in accordance with the present disclosure.

With continuing reference to FIGS. 2A, 2B and 4 throughout, the system400 comprises a DSP 405 that can receive a data stream 410 (e.g., theelectrical digital input symbols in step 205). The DSP 405 isprogrammed, or has sub-modules programmed, to perform the classificationoperation on digital electrical input symbols (e.g., step 210) and thenapply the differential coding operation to only the Class I symbols(e.g., step 215). In some embodiments the DSP 405 is also programmed toperform the holding operation (e.g., step 225), the combining operation(e.g., step 230) and the pre-differential coding operation (e.g., step260).

In some embodiments, the DSP 405 can be embodied in anapplication-specific integrated circuit (ASIC) that includes one or moremicroprocessors, memory blocks, and other circuit components familiar tothose skilled in the arts, that are customized to perform theclassifying, differential coding, pre-coding, holding and recombiningoperations (e.g. steps 210-230 and 260). In other embodiments, theintegrated circuit 405 can be embodied in a general purpose integratedcircuit. In some embodiments of the ASIC or general-purpose integratedcircuit can include one or more microprocessors and memory blocks thatcan be programmed to perform such operations, as stored on computerreadable medium, as computer-executable instructions.

In some embodiments, the DSP 405 is part of a transmitter subunit 420 ofan optical communication system 400. Embodiments of the system 400 canfurther include an optical source 422 and an optical modulator 424.

The optical source 422 can generate an optical beam 426 at a carrierwavelength of light. In some embodiments, the source 422 is a laser,such as a laser diode. In some embodiments, the optical beam 426 can bein any one of the common optical telecommunication bands, including theOriginal (“O”) band (e.g., about 1260 nm to about 1360 nm), Extended(“E”) band (e.g., about 1360 nm to about 1460 nm), Short (“S”) band(e.g., about 1460 nm to about 1530 nm), Conventional (“C”) band (e.g.,about 1530 nm to about 1565 nm), Long (“L”) band (from e.g., 1565 nm toabout 1625 nm) or Ultralong (“U”) band (e.g., about 1625 nm to about1675 nm).

The optical modulator 424 can receive the optical beam 426, and modulatethe optical beam 426 as driven by electrical signals carrying a datastream of the I and Q components of the differential-coded symbol streamfrom the DSP 405. The optical modulator 424 (e.g., an optical IQ opticalmodulator) can generate an optical output signal 428 that emits thein-phase and quadrature pairs of the QDB modulated signals. One skilledin the pertinent art would understand how electrical signals carrying adata stream, e.g. a stream of the differential-coded pairs of symbols asdisclosed herein, can be converted to optical quadrature duobinarymodulated signals by the optical modulator 424.

As illustrated in FIG. 4, the QDB modulated optical output signal 428can carry the information conveyed by the digital electrical inputsymbols (e.g., information received at the data input at step 205) to anoptical fiber 430 or network of optical fibers and amplifiers, and insome cases, carry the output signal 428 over long distances (e.g.,kilometer of longer distances).

As further illustrated in FIG. 4, in some embodiments, to facilitateaccurate transmission of the differential-coded pairs of symbols fromthe DSP 405 to the optical modulator 426 the transmitter subunit 405 canfurther include one or more amplifiers 432 configured to receive andamplify electrical signals corresponding to the differential-coded pairsof symbols.

As further illustrated in FIG. 4, in some embodiments, to facilitateaccurate transmission of the differential-coded pairs of symbols fromthe DSP 405 to the optical modulator 424 the transmitter subunit 405 canfurther include one or more low pass filters 434 (LPFs) configured toreceive the amplified electrical signals output from the amplifiers 432.

As illustrated in FIG. 4, some embodiments of the system 400 can furtherincludes a receiver subunit 440. In some embodiments, the DSP 405 canalso be part of the receiver subunit 440, and in such embodiments, thetransmitter and receiver subunits 405, 440 can be part of, or be, atransceiver of the system 400. In other embodiments, including theillustrated embodiment, the receiver subunit 440 can include a differentDSP 445. The DSP 405, or the different DSP 445, includes an integratedcircuit (e.g., the same circuit in which the DSP 405 is embodied or adifferent circuit) that is programmed to apply a differential decodingoperation (e.g., step 240). The DSP 405, or the different DSP 445,respectively, can also be programmed, or have sub-modules programmed, toperform the choosing operation (e.g., step 235), the combining operation(e.g., step 250), and the post-differential decoding operation (step265) and in some embodiments other modules to perform other operations(e.g., dispersion compensation, carrier separation, demodulation etc.)familiar to those skilled in the art.

In some embodiments of the system 400, the receiver subunit 440 canfurther include an optical-to-electrical receiver 450 configured toreceive as input the optical signal of in-phase and quadraturecomponents of duobinary modulated signals (e.g., differential-codedsymbols transmitted to the receiver subunit 440 as optical signal ofin-phase and quadrature components of duobinary modulated signals 428via the optical fiber 430) and produce as output an electrical signal452 that includes the differential-coded symbols (e.g., [EI_(n),EQ_(n)]symbol pairs) and output electrical signal output data 460 (e.g., dataoutput in step 255) having the differential decoded symbols (e.g.,[EI′_(n),EQ′_(n)] symbols) or post-differential decoded symbols (e.g.,[DI′_(n),DQ′_(n)] symbols).

To facilitate the optical-to-electrical conversion, some embodiments thereceiver subunit 440 can include an optical local oscillator 455connected to deliver a reference optical signal 457 to theoptical-to-electrical receiver 450. Embodiments of the receiver subunit440 can include analog-to-digital converters 462 (ADC) connected to theoptical-to-electrical receiver 450 and connected to deliver digitalelectrical signals 452, including the differential-coded pairs, to a DSP(e.g., DSP 445).

FIG. 4 illustrates another embodiment of the disclosure: anon-transitory computer readable medium 470. The medium 470 comprisessoftware instructions 475 stored on the computer readable medium 470.While shown connected to the DSP 445, the medium 470, or a differentmedium, may provide instructions to the DSP 420. In some embodiments themedium 470 can be in the form of non-transitory memory or firmware inthe DSP 405 or the different DSP 445. In other cases, thecomputer-readable medium can be stored on hard disks, CDs, floppy disks,thumb drive, or other media familiar to those skilled in the art, in acomputer that is remotely located from the DSP 405 and/or the differentDSP 445 but sends the computer-executable instructions to the DSP 405and/or the different DSP 445.

The instructions 475 when processed by the digital signal processor 405,perform a method (e.g., method 200A) that includes processing the inputsymbols representing a data-stream of electrical digital input symbols(e.g., input data 410) including the classification operation 210 andthe differential coding operation 215.

In some embodiments the software instructions 475 include instructionsto perform the holding operation (e.g., step 225), the combiningoperation (e.g., step 230) and the pre-differential coding operation(e.g., step 260). In some embodiments the instructions 475, whenexecuted by the DSP 405 or the different DSP 445, perform thedifferential decoding operation (e.g., step 240). In some embodiments,the software instructions 475 include instructions to perform thechoosing operation (e.g., step 235), the combining operation (e.g., step250), and the post-differential decoding operation (step 265).

The effectiveness of the differential coding and decoding operation asdescribed herein was tested using simulated data. FIG. 5 depicts a plotof bit-error-rate (BER) versus optical signal-to-noise rate (OSNR) foran example data signal using differential-coding anddifferential-decoding for simulated data in accordance with the presentdisclosure. The simulated data signal is configured to represent a 128Gigabyte per second data stream of PDM QDB encoded signals. The opticalsource 422 and local oscillator 455 are assumed to have a 500 kHz linewidth. In the simulation, the Viterbi-Viterbi carrier phase estimationmethod, familiar to those skilled in the art, was used for carrier phaserecovery. As illustrated in FIG. 5, substantially no cycle-slip inducederror propagation is observed as demonstrated by the smooth continuouscurve relationship between BER and OSNR.

Although the present disclosure has been described in detail, thoseskilled in the art should understand that they can make various changes,substitutions and alterations herein without departing from the scope ofthe invention.

1. An oral dosage form of abscisic acid (ABA) or of an in vivohydrolysable ABA-conjugate, for use in a therapeutic, control orprevention treatment of hyperglycemia without a substantial increase ininsulinemia, wherein said dosage form is adapted for the oraladministration of ABA or ABA-conjugate at a daily dose comprised between0.45 μg and 11.4 mg, between 1.5 μg and 6 mg, and between 3 μg and 1.2mg.
 2. The oral dosage form according to claim 1, wherein said abscisicacid (ABA) or ABA-conjugate is contained in a plant extract.
 3. The oraldosage form according to claim 1, wherein said ABA-conjugate ishydrolysable in vivo by hydrolysis of an anhydride, ester or amide bond.4. The oral dosage form according to claim 3, wherein said in vivohydrolysable ABA-conjugate is a conjugate of ABA with a compoundselected from the group consisting of organic acids, inorganic acids,primary alcohols, secondary alcohols, tertiary alcohols,monosaccharides, disaccharides, polysaccharides, biogenic amines andamino acids.
 5. The oral dosage form according to claim 4, wherein saidin vivo hydrolysable ABA-conjugate is ABA-glucosyl ester (ABA-GE).
 6. Afood product comprising an oral dosage form according to claim 1,optionally in combination with one or more further organic and/orinorganic substances, said product being preferably selected from thegroup consisting of carbohydrate-containing human or animal food,healthy products, supplements, sugar-containing energizing beverages,nutraceutical compositions.
 7. Abscisic acid (ABA) or an in vivohydrolysable ABA-conjugate, for use in a therapeutic, control orprevention treatment of hyperglycemia without a substantial increase ininsulinemia, wherein said treatment comprises the oral administration toa subject of an effective amount of abscisic acid (ABA) or ABA-conjugateat a dose comprised between 0.15 and 95 μg/die per Kg of body weight ofthe subject, between 0.5 and 50 μg/die per Kg of body weight of thesubject, and between 1 and 10 μg/die per Kg of body weight of thesubject.
 8. Abscisic acid (ABA) or an in vivo hydrolysable ABA-conjugatefor use according to claim 7, wherein the subject is a human or ananimal and is preferably a healthy, diabetic or pre-diabetic subject. 9.Abscisic acid (ABA) or an in vivo hydrolysable ABA-conjugate for useaccording to claim 7, wherein said therapeutic, control or preventiontreatment of hyperglycemia comprises one or more of the following:improving glucose tolerance without increasing insulin secretion;improving muscle performance and/or endurance; reducing insulinsecretion in response to glucose intake; reducing insulin-dependenttriglycerides synthesis and accumulation thereof, with a resultingimproved weight control after carbohydrate intake.
 10. Abscisic acid(ABA) or an in vivo hydrolysable ABA-conjugate for use in a therapeutic,control or prevention treatment of hyperglycemia without a substantialincrease in insulinemia, wherein said ABA-conjugate comprises an oraldosage form of abscisic acid (ABA) or of an in vivo hydrolysableABA-conjugate, wherein said dosage form is adapted for the oraladministration of ABA or ABA-conjugate at a daily dose comprised between0.45 μg and 11.4 mg, between 1.5 μg and 6 mg, and between 3 μg and 1.2mg.
 11. The use of an effective dose of ABA and/or an in vivohydrolysable ABA-conjugate, said effective dose being comprised between0.45 μg and 11.4 mg, preferably between 1.5 μg and 6 mg, more preferablybetween 3 μg and 1.2 mg, in the preparation of a product as defined inclaim
 7. 12. The use according to claim 11, wherein said ABA-conjugatecomprises an oral dosage form of abscisic acid (ABA) or of an in vivohydrolysable ABA-conjugate, wherein said dosage form is adapted for theoral administration of ABA or ABA-conjugate at a daily dose comprisedbetween 0.45 μg and 11.4 mg, between 1.5 μg and 6 mg, and between 3 μgand 1.2 mg.